This isn't an app store, though. "The content in the store is not apps, but rather links to mobile websites," according to FierceWireless. Smartphone owners visiting the links through Syntonic's service would not be charged with data usage. Syntonic CEO Gary Greenbaum told FierceWireless that Syntonic's technology defines policies for how content is tracked and billed, then translates the policies into network rules. This ensures that data is billed to the "sponsor" rather than the user.

Only 35 pieces of content are in the store for now, but they include some big names like "Airbnb, Amazon, eBay, ESPN, Etsy, Expedia, Facebook, MLB.com, Open Table, Rolling Stone, The New York Times, and Yelp," FierceWireless writes. A closed beta test "will start next week for Android smartphone users. Syntonic is currently inviting people to register for access. An iOS and tablet version of the store will be rolled out over the next few weeks."

AT&T's Sponsored Data was already being used by advertisers who want to exempt their advertisements from counting against customers' data allotments.

Sponsored Data is clearly marked and can be used within both websites and applications, according to AT&T.

"For example, a customer may access an application for healthcare from their insurer. Within the application, there is an educational video," AT&T says. "The customer sees the AT&T Sponsored Data name, identifying that the video is sponsored. When the customer clicks the icon to play the video, the data usage incurred while watching the video is not applied to the customer’s monthly data allowance."

The Sponsored Data scheme has been criticized by consumer advocacy groups who say AT&T is using data caps to "threaten the open Internet" and add to the cost of startups trying to get in front of consumers.